The invention broadly relates to mobile devices of the type utilizing a negative pressure zone between the device and a support surface to produce a zero-gravity effect whereby the device is retained on the surface regardless of the orientation of the surface.
Such devices, while disclosed in the prior patent art as being utilized for a variety of functions, are more particularly associated with mobile toys, for example toy vehicles or the like, which are intended to climb walls or even travel in an inverted position along ceilings. Examples of known devices will be seen in the following U.S. patents:
U.S. Pat. No. 3,810,515 to Ingro, PA0 U.S. Pat. No. 3,926,277 to Shino et al., PA0 U.S. Pat. No. 4,664,212 to Nagatsuka et al., PA0 U.S. Pat. No. 4,926,957 to Urakami, PA0 U.S. Pat. No. 4,971,591 Raviv et al.
Basically, apparatus, normally within the device itself and remote from the support surface, generates a positive air flow perpendicularly away from the surface to create a vacuum or area of negative pressure between the device and the surface whereby the device is retained by ambient pressure which is inherently greater than the pressure in the negative pressure zone.
Such devices to be effective require a proper seal about the negative pressure area or zone to prevent free entry of air into the zone such as would preclude the evacuation of the area and prevent development of the negative pressure. Numerous solutions have been proposed including flexible skirts which ride along and generally conform to the surface, rigid skirts with minimal clearance which, while not eliminating inflow of air, will restrict the flow, and like means.
A problem with known devices is the leakage of air into the negative pressure zone beneath the surrounding skirt which leakage is normally related to the roughness of the surface and irregularities encountered thereon as the device moves thereacross. While the leakage may be minimal when using flexible skirts directly engaging a completely smooth surface, the leakage cannot be completely prevented, and rapidly increases in relation to an increased roughness of the surface. For example, it is unlikely that known devices of this type could effectively traverse a brick or tile wall or an acoustical tile ceiling which include major surface disruptions.